Which of the following was a discovery of edwin hubble?
a. the existence of other galaxies
b dark matter is causing the universe to contract
c. the universe is over 40 billion years old
d. the big bang theory.
e. electron degeneracy of stars

You need to re ask the question with proper

Psychologists often talk of the magical number "7" - so it is generally assumed that we can keep 7 (more or less, so 5-9 is the correct answer) items in our short term memory - we know this as a result of many experiments.

we can increase this by chunking, so for example "7 8 9 5 3" is harder to remember than "78 95 3" - try it yourself!

the answer is a)